Hydraulic system



HYDRAULI C SYS TEM Filed Oct. 29, 1942 INVENTOR WARREN RTUCMER,

ATTORN EYS Patented Nov. 18, 1947 HYDRAULIC SYSTEM Warren R. Tucker, Dayton, Ohio, assignor to The Hydraulic Development Corporation, Inc., Wilmington, Del., a corporation ofDelaware Application October 29, 1942, Serial No. 463,855

3 Claims.

This invention relates to hydraulic systems and, in particular, to hydraulic control systems including a pump of the variable delivery type.

It is an object of this invention to provide a hydraulic system including a variable delivery pump and a restriction, in which means is provided for maintaining the pressure drop across said restriction substantially constant.

It is another object of the invention to provide a hydraulic system including a variable delivery pump and a restricted orifice, in which the pump has associated therewith a control mechanism controlled by the pressure drop across said orifice and adapted to control the pump so as to maintain variations in the pressure drop across said orifice within predetermined maximum limits.

Still another object of this invention consists in the provision of a hydraulic system including a variable delivery pump, in which the pump has associated therewith control means, operable to vary the delivery of said pump, and a restricted orifice having its inlet and outlet hydraulically connected with said control means.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, which diagrammatically illustrates the hydraulic system according to the invention.

In general, according to the invention, a variable delivery pump is provided with first servomotor means including yielding means continuously urging the pump into an increased delivery position, and second servomotor means including a fluid pressure responsive plunger hydraulically connected with a hydraulic system receiving actuating fluid from said pump. This hydraulic system also includes an orifice which has its inlet and outlet hydraulically connected with said second and first servomotor means respectively.

Referring now to the drawing in detail, I designates a variable delivery pump of any conventional design, which may, if desired, be of the radial piston type or of the radial vane type.

The pump is provided with a reciprocable flow control member (not shown in the drawing) which, when moving in one direction, causes increased delivery of the pump, while movement of the how control member in the other direction, reduces the delivery of the pump. The movement of the how control member pertaining to the pump l in one direction is controlled by a plunger 2 reciprocably mounted in a cylinder 3 which is connected to the pump casing 4.

Interposed between the right hand end of the cylinder 3 and the plunger 2 is a spring 5 which continuously urges the flow control member of the pump toward the left so as to increase the delivery of the pump. The cylinder 3 has connected thereto a conduit 6 which leads to a conduit 1. One end of the conduit 1 is connected with a fluid reservoir or tank 8, while the other end of the conduit 1 leads to an orifice, generally designated 9 and of somewhat less cross sectional area than the conduits l and I2. The outlet III of the orifice 9 is connected with the conduit 1, while the inlet ll of the orifice is connected with a conduit [2 which latter is connected with the pressure side l3 of the pump I. The suction side Id of the pump 1 is connected through a conduit I5 and the tank 8.

Branching off from the conduit i2 is a conduit [6 leading into the cylinder I! which is connected, in any convenient manner, to the pump casing 4, Reciprocably mounted in the cylinder I1 is a plunger l8 adapted to shift the flow control member of the pump in a direction opposite to the direction into which the flow control member is urged by the spring 5. In other words, movement of the plunger l8 toward the right, causes reduction in the delivery of the pump I. Inasmuch as, for the understanding of the invention, it is not necessary to show any hydraulic machinery actuated by fluid delivered by the pump I, such machinery has been omitted from the drawing. However, it will be understood that such machinery may be interposed in conduit l2 between the pressure side I3 of thepump l and the branching off point of the conduit 16 from the conduit I2, as indicated at 20. a

The hydraulic system according to the invention operates as follows:

It may be assumed that the pump is in operation and that the spring 5 has shifted the pump into the position shown in the drawing, in which the pump I delivers pressure fluid into the conduit [2. The flow through the conduit I2 is conveyed through the orifice 9 and the conduit 1 to the tank 8, and the pressure created ahead of the orifice 9, by the flow therethrough, is conveyed through the conduit l6 into the cylinder II where it acts on the plunger l8, and it may be assumed that the pressure acting upon the plunger l8, while the latter is in the position shown in the drawing, balances the thrust of the spring 5 ex:

erted upon the plunger 2.

The fluid flows from the conduit l2 through the orifice 9 into the conduit 1 and from there into the tank 8, while fluid is withdrawn from the tank 8 through the conduit IE to the suction side I4 of the pump I.

If it should happen that, due to some circumstances, the rate of fluid flow in the conduit I2 increases, this will immediately result in an increase in the pressure acting upon the plunger I8 so that the latter moves toward the right and thereby reduces the delivery of the pump I. As a result thereof, less fluid will be delivered by the pump l into the conduit I2 so that the pres sure in the conduit I2 created by the restriction at 9, and thereby also in the conduit I6 again drops and the spring again moves the flow,

control member of the pump toward the right until the pressure acting upon the plunger I8 again balances the thrust exerted by the spring 5 on the plunger 2. In other words, the pump delivery will be substantially restored to its previous value so that the pressure at the inlet I I of the orifice 9 will likewise be restored. Consequently, the pressure drop between the inlet II and the outlet III of the orifice 9 will be restored.

Inasmuch as the control action just described immediately follows a variation in the pressure in the conduit I 2,, and is effected in a relatively 9 remains substantially constant.

From the above, it will be clear that the servomotor means pertaining to the pump I tends to maintain a constant pressure drop between the inlet I I and the outlet I0 of the orifice 9.

If the pressure in the tank 8 is higher than the atmospheric pressure, it is preferable to interconnect the right hand end of the cylinder 3 and the outlet Id of the orifice 9. However, if the pressure in the tank 8 is atmospheric pressure, the conduit 6 may be omitted, while the right hand end of the cylinder 3 may be connectedto the atmosphere.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a hydraulic system, a Variable delivery pump having an outlet connected to supply pressure fluid to said system, a first reciprocable member operatively connected with said pump for moving the said pump into increased delivery position, means for continuously urging said first reciprocable member to effect movement of said pump into increased delivery position, a restriction, a second reciprocable member operable by pressure fiuid for moving said pump into reduced delivery position, a first conduit having an end connected to one side of said restriction and its other end connected to the outlet of said pump, a branch conduit connecting said second reciprocable member to said first conduit, an exhaust, and a second conduit connected to the other side of said restriction and to said exhaust, and a second branch conduit connected to said first re ciprocable member and to said second conduit at a point between the other side of said restriction and said exhaust.

2. In a hydraulic system, a variable delivery pump having an outlet connected to supply pres sure fluid to said system, a first reciprocable piston operatively connected with said pump for moving the said pump into increased delivery position, means for continuously urging said first reciprocable piston to effect movement of said pump into increased delivery position, a restriction, a second reciprocable piston operable by pressure fluid for moving said pump into reduced delivery position, a first conduit having an end connected to one side of said restrictionand its other end connected to the outlet of said pump, a branch conduit connecting said second reciprocable piston to said first conduit, an exhaust, and a second conduit connected to the other side of said restriction and to said exhaust, and a secondbranch conduit connected to said first reciprocable piston and to said second conduit at a point between the other side of said restriction and said exhaust.

3. In a hydraulic system, a variable delivery pump having an outlet connected to supply pres sure fluid to said system, a first reciprocable pis ton operatively connected with said pump for moving the said pump into increased delivery position, means for continuously urging said first reciprocable piston to eifect movement of said pump into increased delivery position, a restrie tion, a second reciprocable piston operable by pressure fluid for moving said pump into reduced delivery position, a first conduit having an end connected to one side of said restriction and its other end connected to the outlet of said pump, a branch conduit connecting said second reciprocable piston to said first conduit, said pistons being mounted in opposed relation to each other on opposite sides of said pump, an exhaust, and a second conduit connected to the other side of said restriction and to said exhaust, and a second branch conduit connected to said first reciprocable piston and to said second conduit at a point between the other side of said restriction and said exhaust.

' WARREN R. TUCKER.

REFERENCES CITED The following references are of record in the file of this patent: 

